High order moments of the\bar p p multiplicity distribution in the dual parton model

The first four moments of the \(\bar p\) p multiplicity distribution are computed in the framework of the dual parton model at ISR, SPS collider and Tevatron energies, and for different rapidity intervals. Our results exhibit a striking dependence of the various moments on the size of the rapidity interval which is characteristic of the nature of the rescattering chains in the dual parton model. They also show a violation of KNO scaling throughout the considered energy range. Our results indicate that only light clusters (consistent with known resonances) are produced at all energies.     

A simple event weighting technique: optimizing the measurement of the forward-backward asymmetry of Drell-Yan dilepton and top-antitop pairs at hadron colliders

We describe a simple technique for optimizing the extraction of the forward-backward asymmetry (A _fb) of Drell-Yan lepton pairs (e ⁺ e ^?, μ ⁺ μ ^?) produced in $\bar{p}p$ and pp collisions at hadron colliders. The method employs simple event weights which are functions of the rapidity and |cos?θ| decay angle of the lepton pair. It yields the best estimate of the acceptance corrected parton level ( $\bar{q}q$ ) forward backward asymmetry as a function of final state dilepton mass (M _{? ?} ). Typically, when compared to the simple count method, the technique reduces the statistical errors by 20% for $\bar{p}p$ , and 40% for pp collisions, respectively. The method is equivalent to using the maximum likelihood method, but is much easier to implement. The technique can be used to search for new high mass and large width Z’ bosons which may be best detected through the observation of deviations from the Standard Model expectation for the forward-backward asymmetry. The technique can also be applied in the extraction of the foward-backward asymmetry in the production of top-antitop pairs.     

Baryonic resonance production in\bar p p interactions at 32 GeV/c

The inclusive production of (1232) in \(\bar p\) p interactions at 32 GeV/c is studied using data collected in a bubble chamber experiment with a statistics of ～0.7 events/μb. Total and topological cross sections are evaluated and compared to existing data at other energies. The distributions of reduced longitudinal momentum and rapidity show evidence for some central production. Total cross sections for (∑ ⁺(1385)+cc) and (∑ ^?(1385)+cc) are also presented.     

Wino and zino production inp\bar p collisions: first order supersymmetric QCD corrections

We compute the first order supersymmetric QCD correction to wino \((\tilde W)\) and zino \((\tilde Z)\) production in \(p\bar p\) collisions via subprocesses involving two massless partons inside the nucleon or one massless parton and a massive SUSY parton (squark or gluino). The first order SQCD corrections to the rapidity dependence at CERN collider and Tevatron energies are found large (K～2). The rates are important (～10^?2 nb at \(\sqrt s = 630\) GeV and ～10^?1 nb at \(\sqrt s = 2\) TeV), as soon as the \((\tilde W)\) and \((\tilde Z)\) production by squarks is allowed. Transverse momentum distributions are also given and their shape is found very sensitive to the presence of SUSY partons inside the nucleon.     

The energy dependence of the hard exclusive diffractive processes in pQCD as the function of momentum transfer

We predict the dependence on energy of photo (electro) production processes: γ(γ ^*)+p→V+X with large rapidity gap at small x and large momentum ?t transferred to V in pQCD. Here V is a heavy quarkonium (J/ψ,?) or longitudinally polarized light vector meson (in the electroproduction processes), etc. In the kinematics of HERA we calculate the dependence on energy of cross sections of these processes as the function of momentum transfer t, photon virtuality Q ² and/or quarkonium mass. In the kinematical region $Q_{0}^{2}\le -t\ll Q^{2}+M^{2}_{V}$ the nontrivial energy dependence of the cross section for the vector meson production due to the photon scattering off a parton follows within QCD from the summing of the double logarithmic terms. In the second regime $-t\ge Q^{2}+M^{2}_{V}$ within DGLAP approximation in all orders of perturbation theory the $q\bar{q}$ -parton elastic cross section is energy independent. We show that the correct account of the double logarithmic terms and of the gluon radiation including kinematical constraints removes the disagreement between pQCD calculations and recent HERA experimental data. The explicit formula for the dependence of the differential cross section $\frac{d^{2}\sigma}{dt\,dx_{J}}$ of these processes on $s_{\gamma^{*}N}$ is obtained. We show that perturbative Pomeron type behavior may reveal itself only at energies significantly larger than those available at HERA. In addition we evaluate the energy dependence of DVCS processes.     

Light Hypernuclei Based on Chiral Interactions at Next-to-Leading Order

We present predictions for the binding energies of the light hypernuclei \({^3_\Lambda{\rm H},\, ^4_\Lambda{\rm He}}\) and \({^4_\Lambda{\rm H}}\) based on Faddeev- and Yakubovsky equations in momentum space. We discuss how such results can help to test the existing hyperon–nucleon (Y N) potential models and effective field theory based Y N interactions. Especially, we show results for the chiral interactions at next-to-leading order.     

Energy dependence of {\bar{K}N} interaction in nuclear medium

When the $\bar{K}N$ system is submerged in nuclear medium the $\bar{K}N$ scattering amplitude and the final state branching ratios exhibit a strong energy dependence when going to energies below the $\bar{K}N$ threshold. A sharp increase of $\bar{K}N$ attraction below the $\bar{K}N$ threshold provides a link between shallow $\bar{K}$ -nuclear potentials based on the chiral $\bar{K}N$ amplitude evaluated at threshold and the deep phenomenological optical potentials obtained in fits to kaonic atoms data. We show the energy dependence of the in-medium K ^??? p amplitude and demonstrate the impact of energy dependent branching ratios on the Λ-hypernuclear production rates.     

Rapidity distribution ine + e − annihilation

A method to systematically calculate the rapidity distribution of hadrons in a high-energy jet is formulated in terms of an integral equation for the multiplicity. The distribution has the following properties at high energies: (i) a translational invariance; (ii) an increasingly steep distribution with a width proportional to \(\sqrt {\ln s} \) , but without a widening “central plateau”; (iii) if the rapidity is scaled by \(\sqrt {\ln s} \) , it approaches to a universal exponential curve. In the large rapidity region, however, the translational invariance is broken because of the recoil of the quark by the emission of soft gluons. It is also discussed that a gluon jet has a wider angular distribution.     

Benchmark cross sections forp \bar p collisions at 1.8 TeV

High-energyp \(\bar p\) collisions provide many quantitative tests of the standard model. Of particular interest are “hard scattering” processes, which test not only standard model matrix elements and higher order perturbative corrections, but also the distributions of quarks and gluons in the colliding hadrons. We present detailed comparisons of data from the CERNSp \(\bar p\) S collider with theory, incorporating up-to-date parton distributions derived from recent deep inelastic scattering data. Encouraged by the excellent agreement between data and theory at \(\sqrt s \) =630GeV, we present a complete set of “benchmark” predictions for the FNALp \(\bar p\) collider at \(\sqrt s \) =1.8TeV.     

Forward-backward multiplicity distributions in the Peřina-McGill scheme and analysis ine + e − collisions

A forward-backward multiplicity correlation is considered by the use of the Pe?ina-McGill formula. We obtain analytic formulae for conditional cumulants of the backward multiplicity and a conditional backward multiplicity distribution at a given forward multiplicity. The multiplicity distribution and the conditional mean multiplicity observed at \(\sqrt s = 29\) in HRS ine ⁺ e ^? collisions are analysed. We predict the conditional moments and the conditional backward multiplicity distribution. Those should be compared with the future analyses in HRS.     

Study of inclusive production of π± and protons in\bar p p interactions at 32 GeV/c

Results are presented on the inclusive production of π^± mesons and protons in \(\bar p\) p interactions at an incident antiproton momentum of 32 GeV/c in the MIRABELLE bubble chamber, based on a sample of 55,000 inelastic events. The spectra of π⁺(π^?) andp( \(\bar p\) ) are separated in the whole kinematically admitted region of phase space by a statistical method. The semi-inclusive and inclusive cross sections and the main average characteristics of π andp production are calculated. The invariant differential cross sections are studied as functions of the Fevnman scaling variablex, the rapidity and the transverse momentum. Thex distribution of π^± mesons in the proton fragmentation region does not show any significant contribution from quark exchange or annihilation processes. A possible contribution of hard quark scattering on mesons or baryons is observed for large transverse momenta.     

Extreme \alpha -clustering in the 18O nucleus

The structure of the ¹⁸O nucleus at excitation energies above the $ \alpha$ decay threshold was studied using ¹⁴C + $ \alpha$ resonance elastic scattering. A number of states with large $ \alpha$ reduced widths have been observed, indicating that the $ \alpha$ -cluster degree of freedom plays an important role in this N $ \ne$ Z nucleus. A 0⁺ state with an $ \alpha$ reduced width exceeding the single-particle limit was identified at an excitation energy of 9.9±0.3 MeV. We discuss evidence that states of this kind are common in light nuclei and give possible explanations of this feature.     

Gaugino-Higgsino mixing in selectron and sneutrino pair production

We study \(e^ + e^ - \to \tilde e^ + \tilde e^ - \) together with \(\tilde e^ \pm \) decay emphasizing the importance of neutralino mixing in thet-channel at energies above theZ ⁰ resonance. This illustrated in three different mixing scenarios. Formulae for \(e^ + e^ - \to \bar \tilde v_e \tilde v_e \) are also given.     

Charm production in fixed target experiments

Prompt lepton production in proton beam dump experiments has been critically analysed within the general frame work of \(A_c \bar D\) and \(D\bar D\) production and their subsequent semileptonic decays. Realistic decay modes based on recent experiments are used. We have investigated the effect of using differentx dependences for the charm particles obtained either from simple quark counting rules or as inferred from strange particle production data. The \(D\bar D\) production is assumed to have a linearA dependence and for the \(A_c \bar D\) process bothA ¹ andA ^2/3 dependence is used. We show that by a simultaneous fit to the energy and angular distributions of prompt leptons in all the experiments the ratio of \(A_c \bar D\) to \(D\bar D\) production cross section can be determined. A comparison of this fit with these experimental distributions indicates that thex dependences based on strange particle data are strongly favoured. AnA ^2/3 dependence for \(A_c \bar D\) production, which corresponds to a quasi-diffractive process, is favoured although within existing errorsA ¹ dependence cannot be ruled out. Putting together the cross section results from our analysis with other results at similar energies (p _1ab ～400GeV/c) the production cross sections ( \(A_c \bar D\) ) and ( \(D\bar D\) ) are estimated to be ～25 and ～20 μb/nucleon respectively leading to a total inclusive charm cross section of ～90 μb/nucleon.     

Invariant-mass distributions for the pp \rightarrow pp \eta reaction at Q = 10 MeV

Proton-proton and proton- $ \eta$ invariant-mass distributions and the total cross-section for the pp $ \rightarrow$ pp $ \eta$ reaction have been determined near the threshold at an excess energy of Q = 10 MeV. The experiment has been conducted using the COSY-11 detector setup and the cooler synchrotron COSY. The determined invariant-mass spectra reveal significant enhancements in the region of low proton-proton relative momenta, similarly as observed previously at higher excess energies of Q = 15.5 MeV and Q = 40 MeV.     

Evidence for hybrid mesonsQ\bar QG

We point out that the recent CESR data on γ(5 S) and γ(6 S) show evidence for \(b\bar b\) and \(b\bar bg\) mixing. We show that ψ(4159) and ψ(4030) are not2D and 3S, \(c\bar c\) states but mixtures of 3S, \(c\bar c\) and \(c\bar cg\) states. We show various ways to find further evidence for hybrid states experimentally.     

Kaon production in\bar pp interactions at c.m. energies from 200 to 900 GeV

A detailed analysis ofK _s ⁰ production in \(\bar pp\) |<2.5 the average transverse momentum is found to be 0.53±0.07 GeV/c at 200 GeV and 0.62±0.08 GeV/c at 900 GeV, which is an increase with respect to data at c.m. energies below 60 GeV. TheK _s ⁰ production cross sections in inelastic collisions are 29±4 mb at 200 GeV and 63±6 mb at 900 GeV, showing an increase compared to lower energy data. The central kaon density is found to increase as a logarithmic function of energy. At 900 GeV, where statistics are sufficient to allow one to draw conclusions, the average transverse momentum is higher in events with large charged multiplicity than in events with low multiplicity.     

Electron (positron) impact excitation (2p state) of lithium at intermediate energies

In this work, studies have been carried out to investigate theoretically the electron (positron)-impact-induced 2s → 2p lithium (Li) transition at 20 and 60 eV using the coupled-channel optical method (CCOM). The inelastic differential cross sections (DCS) together with the reduced Stokes parameters ( $\bar P_1$ , $\bar P_2$ , $\bar P_3$ ) and other parameters such as the alignment (γ, $\bar P_l$ ), orientation (L _⊥) and coherence parameters (P ⁺) are reported in the present calculations. Comparison is made with other available theoretical and experimental measurements.